1. Field of the Invention
The present invention relates to a portable power driven tool such as a portable circular saw and particularly to a portable power driven tool which is used by an operator with a tool body grasped with both hands.
2. Description of the Prior Art
A conventional portable power driven tool such as a portable circular saw includes a body, a handle mounted on the body, a motor disposed within the body, a switch for starting the motor and a trigger for operating the switch. The switch is turned on or off by pushing the trigger when the handle is grasped or by subsequently releasing the trigger. The operation of the switch to turn on and subsequently to turn off is performed in each cutting operation. In such a portable power driven tool, the trigger may be accidentally pushed to turn the switch on so as to start the motor when the tool is in its standby condition for subsequent cutting operation after a first operation has been finished.
For preventing the trigger from accidentally being pushed, it has been proposed to provide lock means in the vicinity of the trigger. The lock means prevents the trigger from being pushed unless it is released from its locking engagement.
U.S. Pat. No. 3,245,439 discloses a portable circular saw having a trigger of conventional type. U.S. Pat. No. 4,516,324 discloses a portable circular saw having a handle and a handgrip portion intended to be grasped with both hands.
However, in a power driven tool such as a portable circular saw of the type intended to be grasped with both hands of an operator for cutting operation for example, the trigger may be pushed or released by one hand of the operator with the handle grasped in only that hand to turn the switch on or off. The trigger may be operated by one hand even if the above lock means has been provided for the trigger or the switch. Also, the trigger can be operated independently of grasping of the other grip portion in another hand. Thus, the tool is occasionally used by grasping in only one hand, departing from the intended mode of use or use by grasping with both hands and the function of the tool cannot be fully exhibited.